Mild to moderate knee osteoarthritis causes peripheral and central pain sensitization and reduced quality of life

The purpose of this study was to determine if individuals with mild to moderate knee osteoarthritis (OA) experience hyperalgesia and central sensitization by comparing them to healthy age and sex-matched control subjects and to determine if levels of hyperalgesia and central sensitization are associated with pain intensity at rest and during movement. A secondary purpose was to determine if these individuals experience significantly poorer quality of life than healthy subjects and if pain and function predict their quality of life. Seventy-five knee OA subjects and 25 age and sex-matched healthy controls were enrolled. Quantitative sensory tests (QST), including punctate pain intensity (PPI), pressure pain threshold (PPT), heat pain threshold (HPT), heat pain tolerance (HPTol), and heat temporal summation (TS), measured primary and secondary hyperalgesia and central sensitization. Pain intensity at rest and during movement was assessed on a 10 cm Visual Analog Scale, walking function was measured with the Timed Up and Go (TUG) test and the Medical Outcomes Study Short Form 36 (SF-36) measured quality of life. Significant differences were found for PPI at proximal and distant sites, for PPT and TS at the affected knee, and for all SF-36 scores. QST measures were significantly related to pain intensity at rest and during movement. Pain, but not function, predicted quality of life in knee OA subjects. This study shows that individuals with mild to moderate knee OA are already experiencing peripheral and central pain sensitization which relates to the level of perceived pain. These individuals also have a reduced quality of life which is predicted by the level of perceived pain. These results suggest that aggressive pain management during this early period is indicated to improve the quality of life for these individuals who are not yet candidates for joint replacement.